1. Field of the Invention
The present invention relates to a method of operating an optical recording apparatus, and more particularly, to a method of setting the optimum recording power using characteristic values calculated inversely from a recording power level that allows a recordable optical disc to have a minimum value of jitter.
2. Description of the Related Art
Development of recordable discs has resulted in advances in the technologies of storage media such as an optical disc. The recordable discs include a compact disc recordable/rewritable (CD-R/RW) and a digital versatile disc recordable/rewritable (DVD±R/RW).
Unlike read-only optical discs, use of the recordable discs requires complicated recording algorithms. That is, the level of the recordable disc technologies is higher than that of the read-only disc technologies. For instance, levels of the recording power must be defined to record data on a recordable disc. The recording power influences recording and reproducing qualities, and thus, standards of recording power have been prescribed. However, in fact, it is impossible to indiscriminately set recording power since the recording power is determined by the performance of an optical disc and a recording apparatus. For this reason, during a write operation, the recording apparatus detects and uses an optimum recording power for an optical disc. A method of detecting the optimum recording power is standardized, which is referred to as optimum power control (OPC).
Optimum power control will now be described briefly. In general, information regarding reference recording power is described in a region of an optical disc, e.g., a lead-in region, and a recording apparatus performs a test for detecting the optimum recording power in a particular region or section of the optical disc based on the information. The test for detecting the optimum recording power is referred to as power calibration (PC), and the particular region or section where PC is performed is referred to as a power calibration area (PCA). In other words, the recording apparatus performs the test a predetermined number of times to obtain its optimum recording power that is also fit for the type of an optical disc. In general, in the test, values of the recording power are stored in the PCA from the bottom level upward or vice versa. Then the test values are reproduced and a recording power value, allowing a desired reproduction quality, is selected and set as the optimum recording power.
FIG. 1A illustrates a region of a CD-RW where optimum power control is performed. In detail, a PCA is positioned before a lead-in region formed in an inner part of the CD-RW, and divided into a PCA test section and a PCA count section. Before performing a write operation, a recording apparatus checks the PCA count section to detect the PCA test section. Next, the recording apparatus performs power calibration for optimum recording power in a predetermined part, e.g., 15 sectors, of the detected PCA test section. After power calibration, the result of power calibration is marked in the PCA count section so that it can be referred to in a next write operation, thereby making it easy to detect the PCA test section in a next write operation.
FIG. 1B illustrates a region of a DVD±R/RW, which has a higher recording density than a CD-RW, where optimum power control is performed. Referring to FIG. 1B, there is an unused part of a PCA that is an inner part of the DVD±R/RW, a size of the unused part ranges from 1 sector to several tens of sectors. In the case of the DVD±R/RW, test data recorded in the PCA is reproduced and radio-frequency (RF) processed to obtain an RF signal, characteristic values of the RF signal are calculated, and optimum power control is performed using the characteristic values. Optimum recording power of the DVD±R is detected using a value β that indicates a degree of asymmetry of the RF signal, and the optimum recording power of the DVD±RW is detected using a value γ obtained by differentiating a modulation value or modulation characteristics of the RF signal. However, the value β and the modulation value may vary according to a media manufacturer, the type of an optical disc, or conditions of a pickup of a disc drive performing a write operation. Accordingly, during a manufacture process, a media manufacturer tests an optical disc to measure the value β and the modulation value (or the value γ) and stores them in a table in firmware in the optical disc, so that optimum power control can be performed using time information or an identifier (ID) read from the optical disc and the values stored in the table.
However, as optical discs that have the same time information or ID but have different writing/reading speeds or media, come onto the market, it is difficult to set optimum recording power for various types of optical discs using the value β and the modulation value.